Experimental Investigation of the Pressure and Water Pressure Responses of an Inclined Shaft Wall During Grouting

A scale model test with a geometric scale of 1:20 was carried out to simulate chemical grouting in a geological prototype of the auxiliary inclined shaft of the Jinjitan coal mine, Shaanxi Province, to address water and sand inrush accidents. The pressure responses in the surrounding sand layers to grouting of an inclined shaft was experimentally investigated using soil pressure and pore water pressure sensors. Grout propagation was observed by slicing the stabilized mass after grouting. The results show that grouting of the roof, side wall, and floor of the inclined shaft caused pressures to both increase and decrease; after the slurry fully gelled, the pressure on the roof and side wall of the inclined shaft was effectively released, but accumulated on the floor. The water pressure on the roof and side wall of the inclined shaft went through three stages: low amplitude fluctuations, high amplitude fluctuations, and a sudden drop. The floor water pressure experienced stages of pressure fluctuation, maintenance, and recovery. The propagation and solidification of the slurry increased the pressure on the shaft wall. By analyzing the solidified grouted mass, we found that contact among particles within the penetration radius can be classified into three types: a gelled slurry skeleton, an integrated granular particle and slurry skeleton, and a granular particle skeleton. Moreover, the reinforcement mechanism of grouting is mainly fracturing and permeation. The results imply that the designed grouting pressure in the floor should be slightly less than in the roof and side wall to avoid secondary failure of the floor. During actual grouting, fracturing occurs first under high grouting pressure, while permeation occurs as grouting pressure decreases.